Electric arc apparatus



April 22, 1941. H. G. SPEAR ELECTRIC ARC APPARATUS Filed April 8, 1940 5 Sheets-Sheet 1 W Y R5 E 0' m m6 0 w w N A 4 April 22, 1941. H. s. SPEAR ELECTRIC ARC APPARATUS Filed April 8, 1940 5 Sheets-Sheet 2 pnz.

IN VENTOR 4 TTORNE Y April 22, 1941. SPEAR 2,238,918

ELECTRIC ARC APPARATUS Filed April 8, 1940 5 Sheets-Sheet 3 f2! 1Z0 INVENTOR Han 414 0 6 5254/? 1a May 119 120a ATTORNEY April 22, 1941.

H. G. sPEAR I 2,238,918

ELECTRIC ARC APPARATUS Filed April 8, 1940 5 Sheets-Sheet 4 I N V E N TOR. Hana/Pa 6. 5 54 ATTORNEY.

April 22, 1941. H. s. SPEAR ELECTRIC ARC APPARATUS Filed April 8, 1940 5 Sheets-Sheet 5 IN VEN TOR. Haw/4P0 6. 5 54 ATTORNEY.

Patented Apr. 22, 1941 UNITED STATES PATENT OFFlC ELECTRIC ARC APPARATUS Application April 8, 1940, Serial No. 328,463

21 Claims.

My invention relates to electric arc apparatus wherein two carbon electrodes are fed to the arc by means of negative and positive heads and has particular reference to searchlights wherein such heads are mounted in a casing having a reflector at the back thereof. Heretofore, where the reflector casing is quite large, say 60 inches in diameter, it has been proposed to mount the heads on a support provided by the bottom of the reflector casing and to provide a motor to drive both heads.

One object of my invention is to simplify the power drive from the motor for operating the heads. Another object is to reduce the shadow or projected area thereof on the mirror so as to increase the light reflected from the mirror, in case the heads, the support therefor, the motor and its driving connections are all arranged in front of the mirror.

Heretofore, it has been proposed to close the front of the reflector casing with a pane of plane glass having an aperture in the center thereof through which the positive electrode is adapted to pass. In order to provide access to the working parts.-a manhole has heretofore been provided in the side of the reflector casing.

A further object of the invention is to provide an improved arrangement for feeding the positive and negative electrodes by hand, from a position exterior of the reflector casing. Y

The positive head is provided with feed wheels for feeding the positive electrode. Another object of the invention is to release these feed wheels from a point outside of the reflector casmg.

Heretofore, a slide has been provided for both the positive and negative heads so that they can be reciprocated as a unit along the axis of the mirror in order to bring the-arc to the focal point of the mirror. A further object of the invention is to provide an improved mount for the negative head on the slide so as to increase the intensity of the light projected from the crater of the positive electrode to the mirror.

a cam. A further object of the invention is to improve the shape of the cam to increase the latitude of the feed.

A further object of the invention is to strike the arc quickly and without prolonged hunting of the negative electrode in seeking its operating position.

For further details of the invention reference may be made to the drawings wherein:

Fig. 1 is a side elevation with certain parts broken away and other parts in cross section of electric arc apparatus according to the present invention.

Fig. 2 is a front elevation of the apparatus of Fig. 1.

Fig. 3 is a sectional view on lines 3-3 of Fig. 2, looking in the direction of the arrows.

Fig. 4 is an enlarged vertical sectional'view of part of the power drive for the negative electrode drive shaft. I

Fig. 5 is a plan view partly in section of the clutch mechanism in Fig. 4.

Fig. 6 is an enlarged vertical cross sectional view of the positive head.

Figs. 7, 8, 9, 10, and 11 are sectional views on lines '|-l, 8--8, 9-9, Ill-l0, and ll--ll respectively of Fig. 6, looking in the direction of the arrows.

Fig. 12 is a sectional view on line I2-I2 of Fig. 9, looking in the direction of the arrows.

Fig. 13 is a sectional view on line I3-l3 of Fig. 6, looking in the direction of the arrows.

Referring in detail to the drawings, the arc apparatus generally represented. at is shown as being mounted inside of a reflector casing which is known in the art. This casing comprises two cylindrical sections 2 and 3 bolted together at 4 and having a concave mirror not shown in the concave back 5 and of the same diameter as casing 2 and 3. The casing 2 and 3 has a plate glass front 6, provided with a central aperture 1 through which the positive electrode 8 passes. The casing section 3 has four apertured bosses 9 which support the arc apparatus including motor I09 and strike coil I96, as a unit. Base plate I0 is secured to the bosses 9 by bolts ll. Plate I0 is flat and has sides which are cut away, as shown in Fig. 3. On plate It) are mounted two spaced columns l2 and I3, each of which comprises an open grid as shown in Fig. 1, to reduce weight. The columns l2 and i3 are arranged edgewise toward the end of the casing 5. so as to cast a minimum of shadow on the mirror not shown, and are spaced crosswise of the axis of the positive head 25. Columns l2 and I3 incline toward and project over the casing section 2. as shown in Fig. 1. Column 52 at the bottom thereof has apertured feet l4 and I5 which rest on plate Ill and which are secured thereto by bolts I6 and I1. Similarly column 53 has apertured feet M3 resting on base it and secured thereto by bolts l5 and 25. As shown in Fig. 7 columns l2 and i3 support at the tops thereof a bed H to which those columns are secured by bolts 22 and 23. Bed 2i has a tongue and groove connection with slide 25 on which the positive head 25 and the negative head 25 are mounted, as shown in Fig. 1. As shown in Figs. 6 and 7, underneath slide 26 is a nut 2i secured to slide 24 by bolt 28. Nut 27] has screw threaded engagement with screw 29 which is rotatably mounted in lugs and 3t underneath bed 2i. On screw 29 between lugs 35 and ti is a fixed spiral gear 32 meshing with spiral gear 33 fixed to and mounted on shaft 55 which is rotatably mounted in bearings 35 and 55 at the top of the columns l2 and l3 respectively. Shaft 34 as shown in Fig. 2 has a coupling 35 and is rotatably mounted in bearing 35 in the side of the casing 2. a handle 37 so that it may be rotated from a point outside of casing 2 in order to reciprocate the slide 2 3 to focus the are produced by the positive carbon 8 and the negative carbon 59.

As shown in Fig. 6, slide 24 has a raised base All to the top of which the section-(ll of the positive. head 25 is connected by bolts 52 and 53 which are insulated from section ll by insulation 42 and 33' respectively. Section M is insulated from base by insulation 55'. Casing M of the positive head 25 surrounds and is fastened to the section M by means of bolts 35 and 55 as shown in Fig. 8. The electrode feed apparatus of the positive head 25 as shown in Fig. 6 in several respects is like that shown and described in the United States patent to Anderson-2,173,149, patented September 19, 1939. Section ll, as shown in Fig. 6, has a fiat end wall t? which has a central aperture 58 for the electrode 5. To wall All is fastened a disc 55 of insulating material by means of bolts like 55. Countersunk in the insulating material 39 are bolts like to secure terminal block 52 which has heat radiating flanges 55. Secured to terminal block 52 by means of screws like 5 is a fianged metal disk 55 which carries a disk 55 of carborundurn or other heat insulating material. Terminal block 52 has a central bore for the electrode 5 and so has disk The disk 55 is provided with a plurality of heat radiating apertures 5?.

Terminal block 52 at the bottom thereof has a radial aperture 58 in which is slidingly mounted pressure shoe having a reduced elongated portion 55 which slides in tubes 5i. As shown in Fig. 10, the bottom of terminal block 52 is cut away on substantially a horizontal line, as shown at 52, and has secured thereto a block 53, having a cylindrical bore in which the tube 5H is mounted. Tube 55 is secured to block by soldering or otherwise. In the bottom of tube is mounted a spring 65, tension of which can be adjusted by the screw 55 threaded into the end of tube iii to vary the pressure of shoe 59 on the electrode 5. a spring follower to remove and protect the spring 55 from the heat of the electrode 5 and reduce the danger of such heat from causing spring 55 to loose its temper. Block 53 is secured to terminal block 52 by bolts fill and 55 which also clamp the ends of electrical conductors 55 and 55 which may be of silver strip, between the terminal block 52 and block 53. Conductors 59 and it are curved to facilitate expansion due to the heat of the arc, and the lower ends thereof are secured by bolts ii and M respectively, to the Shaft 34. is provided with The elongated portion 55 serves as opposite ends of a U shaped bracket l3 insulated from slide 25 by insulation it and secured thereto by bolts insulated from slide 24 by insulation '56. Bolt ll secures the upper end of a flexible conductor ll! which is electrically connected to a. conductor 55 and through bracket 13 to conductor ill. The upper ends of conductors 69 and 715 of course are in electrical contact with the terminal block 52.

Referring to Fig. 6, the positive electrode 8 is fed longitudinally at certain times under control of feed wheels l5, meshing with scroll gear 19 having teeth engaged by screw Bl which reciprocates with a follower 82 riding on cam 83 as set forth in the above mentioned patent, However, I provide a greater latitude of feed by giving this cam the shape of an eccentric as shown in Fig. 8. As shown in the patent, the cam has three lobes, each having an extended surface concentric with the axis of the head. Still referring to the patent, no feed of the electrode takes place while cam follower is in engagement with those concentric surfaces, and even though the number of lobes were reduced to one, there would still be a substantial length of time during which no forward feed of the electrode could take place. Also, it has been found that the flattened portions M55, in Fig. 6 of the patent, are at such an angle that at times the screw will strike and skip one or two serrations before it engages a s'erration firmly enough to hold the scroll gear stationary. These defects are overcome by the eccentric cam 85 secured to gear 84'. by bolts 55', in Fig. 8, wherein the screw 59 will not skip and wherein the electrode 8 may be fed forward for a complete revolution of the arc feed apparatus or any desired fractional part of a revolution. The surface of cam 83 is a true eccentric. Namely,it is a complete circle having a center abaxial of the center of rotation of gear 85 on which cam 83 is mounted.

Gear 55 is preferably a worm gear and, as shown in Fig. 9 it meshes with a worm 85 having an axis of rotation at right angles to the axis of P rotation of worm gear 85. The casing section 44 of the positive head 25 is provided with an extension 55 which houses the Worm 85 and which supports the latter at its opposite ends in bearings 55 and 58. Worm 55 is connected through a suitable removable coupling 55 to the section 95 of the positive electrode drive shaft mounted in bearing 52 carried by bracket 52 secured by screws 93 and 5 to the slide 2 3. Shaft section 95' is coupled through removable coupling a (see Fig. 12) to the shaft section at. Shaft 90' has fixed thereto a bevel gear 55 meshing with a similar gear on the hand operating shaft 9i mounted in bearing 98 in bracket 92.

As shown in Fig. 2, shaft 9? has a universalcoupling and a slidable coupling Mill and is mounted at its outer end in a bearing Mill in the wall of casing 2. Shaft fll outside of casing 2 is provided with a handle N12 to feedthe positive electrode 8 by hand. Shaft 95 has a universal coupling r155, a slidable coupling housing a compression spring [1550; and a frictional coupling (155 like the frictional coupling m5 later nected from the mirror not shown, motor I06 is arranged endwise towards the mirror, in other words, its shaft and axis are parallel to the axis of easing 2. Also such interference is reduced by reason of the fact that motor I09, in being mounted on plate I which rests practically on the bottom of casing 2, is removed practically as far as possible from the axis of casing 2. Such reduction of interference is also increased due to the use of a compact reduction gearing III, having a ratio of about 60 to 1, and mounted on and carried by the end of motor I09, and by the further fact that this reduction gearing III in being arranged at the end of the motor is in effect behind the motor so far as light reflected from the mirror is concerned. Slow speed shaft I01 which is driven by the reduction gearing III extends on opposite sides of the axis of motor I09, the lower extension II2 having mounted thereon an eccentric H3 which cooperates with the follower II4 (see Fig. 3) The follower II4 oscillates lever II5 which is pivotally mounted intermediate its ends to the base I0 at II6. Lever H5 at its other end is connected through link I I1 to lever arm I I8 rotatably mounted on shaft II9 (see Fig. 4). Shaft H9 is rotatably mounted in bearing I20a in the base I0. Ball bearing I20 rests on bearing I200 and takes up the thrust of disk I24 and the elements resting on it including the universal coupling I55 which is pushed downwardly by compression spring I56a in coupling I56. Lever arm I I8 has an eccentric groove I2I in which rides the ball I 22 which also rides in groove I23 in the clutch disk I24 fixed to shaft II9. Ball I22 is urged to the right, as shown in Fig. 3 by spring I25. When clutch arm H8 is moved counterclockwise, ball I22 is wedged between clutch arm I I8 and disk I 24 to rotate the disk I24 with clutch arm I I8. When clutch arm I I8 rotates in a clockwise direction, ball I22 Is moved slightly towards the wide portion of groove I2I by the cam action of that groove and it does not couple lever arm H8 to disk I 24. Shaft H9 is thus rotated stepby-step as lever II5 oscillates. The amount of the step-by-step movement and therefore the speed of shaft H9 is regulated by the adjusting screw I26 in threaded engagement with post I21 mounted on base I0. The top of post I21 has secured thereto one end of a tension spring I26, the

other end of which is connected to lever II5 as shown in Fig. 3, in order to return lever II 5 to a normal position against the screw I26.

As shown in Fig. 4, shaft H9 is coupled by the frictional coupling I06 to shaft I29 rotatably mounted in bearing I30 at the top of support I3I i which is secured to the base I0 by bolts I32 and I33, as shown in Fig. 3. The coupling I06 comprises a cup shaped member. I34, which is secured by screw I35 to an inner member I36 fixed at I31 to shaft I I 9. Between the bottom of member I36 and the top of ratchet arm H8 is a washer I38. The member I34, at diametrically opposite points, has apertures I39 and I40 which are slightly smaller than the balls I and I42 which are urged outwardly by spring I43. The balls I and I42 and spring I43 are housed in a bore I44 at right angles to the axis of the coupling member I45, which is fixed to shaft I29 at I46.

Frictional coupling I06 permits shaft II9 to remain stationary, and shaft'l29 to be rotated by the handle I41 in Fig. 2 to feed the negative electrode by hand. The support I3I carries an extension I48 which houses a hollow adjusting screw I49, which in turn, houses a spring I50 bearing on plunger I 5| which bears against disk I52, fixed to shaft I29 at I53 and I54. The spring pressed plunger I5I serves as a frictional brake to prevent overthrow of the ratchet II8. Shaft I29 has a universal joint I55, as shown in Figs. 1 and 2, connected through a slidable coupling I56 (Fig. 1) to shaft I51 which has a universal coupling I58 with shaft I59 rotatably mounted in the horizontol portion of slide 24, and in the bearing I630, and bracket I63. Below slide 24, shaft I59 has fixed thereon a gear I60 meshing with gear I6I mounted on shaft I62 (Fig. 2), the inner end of shaft I62 being mounted in a bracket I63 which depends from the underside of slide 24, as shown in Fig. l. Shaft I62 has slidable coupling I62a, shaft I62 and universal coupling I62b and the outer end thereof rotatably mounted in a bearing I64 in the side of casing 2. Shaft I59 is rotatably mounted in slide 24, as indicated at I65, and it extends through slide 24 and is also rotatably mounted as indicated at I66, in the bracket portion I61 of the negative head 26. Shaft I59 at its top has fixed thereto a gear I68 which meshes with gear I69 mounted on the smooth shaft end I10 of screw "I. The shaft I10 is provided with a slot I12 in which extends a pin I13 fixed to gear I69 also mounted on the end of shaft I10 which is rotatably supported by a bearing I14 which bears at one end against the bracket I61 and at its other end against gear I69 to keep gear I69 from sliding longitudinally on shaft I10 while permitting shaft I10 to slide in it. The collar of gear I69 rests against bracket I61. The horizontal portion-of slide 24 terminates at its rear in a depending portion I15 to which the bed I11 of negative head 26 is secured by bolts like I16. The axis of the negative head 26 is arranged at approximately 50" to the axis of the positive head 25, as I find this gives improved illumination from the arc.

Bed I11 carries a slide I18 which has screw threaded engagement with screw I1I. Insulated from slide I16 by insulation I19 is a top member I66 secured to slide I18 by insulated bolts like I6I. Member I60 carries a clamp I82 operated by wing nut I63 to clamp the end of the negative electrode 39. The screw "I at its lower end is also smooth to provide a shaft I84 which slides in the bearing I carried by the bed I11. Shaft I64 terminates in a collar I86 engaged by one end of a lever I61 pivotally mounted at I88 to an arm I69 extending from the bed I 11. The other end of lever I61 is pivotally connected at I90 to coupling III which has screw threadedengagement with the strike rod I92, the lower end of which is screw threaded to coupling I93 pivotally connected at I94 to the armature I95 of the strike coil I96. Armature I95 is pivoted at I91 to a bracket I96 of magnetic material, the base I99 of this bracket supporting the coil I 96 and its core 266 and being suitably secured by means not shown, to the base I0. The armature I95 is controlled by spring 2" connected at one end to base I 6 and at the other end to an adjusting screw 202 mounted in the projecting end of armature I 95.

As shown in Fig. 2, coil I96 has a lower terminal 203 connected to the lower end of a rigid conductor 204, and an upper terminal 201 connected to an insulated post 208 mounted in the base I0. The post 208 is connected to one side of a power line 209. The conductor 204 throughout its length is arranged behind the flange 206 on the column I2, to eliminate or reduce the shadow cast by conductor 204 on the mirror. The upper end of conductor 204 passes through an aperture in column I2 and is insulated from but mechanically secured thereto bynuts such as 205. The upper end of conductor 2% is electrically connected to the lower end of flexible conductor 11 by nut :10. g

In order that the operator from a point outside of easing may be able to release the feed wheels 18 from the positive electrode 8, the following arrangement is provided. Part of this arrangement, namely the mechanism adjacent feed wheels 18, is similar to the mechanism described in my co-pending application 5. N. 313,729 filed January 13, 1940, for Are apparatus. As shown in Fig. 6, scroll gear "it is frictionally mounted on sleeve 2M, which is rotatably carried by a bearing 2M. Sleeve til is secured by a set screw (not shown) to the hub of the drive gear 84. Sleeve 2i i has a retaining nut 283 which bears against bearing 2H2. Slidably mounted inside of sleeve 211i is a tube 2M which carries a disk 2l5 secured thereto by set screw 2M5.

As shown in Fig. 13, sleeve 2M has an operating head 2!! having cross slots 208 and 2m in which the shafts 22d and 22H of the feed wheels l8 are mounted. The shaits have secured thereto tension springs 271iand 2222 which urge the feed wheels l8 against the electrode 8, these ieed wheels extending through longitudinal slots 223 and 224 in the head 20?] and also extending through similar slots 2% in thetube did. The opposite sides of the head all] are flat as shown in Fig, 13, and against these sides rest the wedge plates 225 and 22'l, the narrow ends of which are pivotally mounted on pins 228 and 229 carried on the opposite sides of the head 230 on the tube 2. Tube 2 it is slidably mounted in sleeve 2. When tube 2M is moved to the right as shown in Fig. 6, the wedges 22b and Hi engage the shafts 220 and 22H to move the feed wheels I8 outwardly away from electrode 8. Tube it is moved to the right by means or the rotatable cam or eccentric 236 (see Fig. ll) which bears on the disk 2l5 which is mounted on tube 2.

Disk 2l5 is enclosed by a housing 232 (Figs. 6 and 11) which is secured to the casin 44 by bolts like 233. Housing ctr has an aperture 234 for the electrode 8 and at the side thereof as shown in Fig. 11, it also has a bearing 235 for a shaft 236 which carries the earn 230. As shown in Fig. 2, shaft 236 is connected through a universal coupling 23F and a slidable coupling 238 to the shaft 238 which is rotatably mounted in a bearing 24!] in the wall of easing 2. Outside of casing 2, shaft 239 is provided with a knob 243 so the operator can turn shaft 239 and re= lease the feed wheels 778 from the electrode 8. Tube 284 is urged to the left as shown in Fig. 6, by the shafts 220 and 220 acting under the force of springs 2H and 222 on the inclinediaces of the wedge plates 2% and 2277.

As shown in Fig. 1, current is, fed to the negative electrode 39 by a flexible conductor 2412, which has its lower end connected to the upper end of a rigid conductor As shown in Fig. 2, the ends of conductor 2 33 project through the column i3 and are secured thereto by insulation,

not shown, and by nuts such as Zfld-and 2.45. The rigid conductor 2G3 throughout. its length is arranged behind the flange M6 on the column l3, as described in connection with rigid conductor 204. The lower end of rigid conductor 243 is electrically connected to one side of a power line 241, the other side of this power line being 209. Motor the has one terminal thereof connected by conductor 268 to the line Ml, and the other terminal connected by the line 249 to the terminal 203 which has a potential substantially the same as that of terminal 209, as the voltage drop in coil I 96 is very low.

It will be apparent that I have provided a compact arc-light unit which may be readily installed inside oi a. searchlight can and wherein the following operations may be made from a remote point, i. ,e. outside of the can: release of feed wheels 18 by means of knob 2, feed of positive electrode 8 by means of handle I02, feed of negative electrode 39 by means of handle 1, and focusing adjustment of the are by means of handle 37. The slide couplings 238, I00 and I62A, also the universal couplings 231, 99, I623 permit the slide 24 to be operated for focusing purposes.

I claim:

1. Arc apparatus comprising the combination of a cylindrical wall having bosses projecting from the inside of said wall, a base removably secured to said bosses, a pair of spaced columns arising from and secured to said base, positive and negative electrode heads, means at the top of said columns for supporting said heads, a motor on said base between said columns, and means coupling said motor to said heads.

2. Arc apparatus according to claim 1 comprising a strike coil on said base behind said motor.

3. Arc apparatus according to claim 1 wherein said means coupling said motor to one of said heads comprises stepping mechanism on said base.

4. Arc apparatus comprising the combination of an electrode head, a motor having a reduction gearing, shaft means coupling said gearing to said head, said shaft means comprising a frictional coupling between said gearing and said head, and manual meansfor operating said shaft means between said coupling and said head.

5. Arc apparatus comprising the combination of a positive head having a casing, a slide supporting said casing, feed mechanism in said casing comprising a worm wheel having an aperture through which the electrode is adapted to pass, a worm meshing with one side of said worm wheel and arranged with its axis at right angles to the axis of said worm, means on said casing for supporting said worm at opposite ends thereof, a motor driven shaft connected to said worm, a bearing for said shaft, a gear fixed to said shaft, a hand operating shaft having a gear meshing with said last mentioned gear, a bearing for said hand operating shaft, and a bracket on said slide for supporting said bearings,

6. Are apparatus comprising the combination of a reflector casing, a base mounted in the bottom of said casing. a support arising from said base, a slide at the top of said support, a positive electrode head on said slide, feed wheels in said head, means operable to release said feed wheels, remote control means operable from the exterior of said casing for operating said means, and a motor on said base having a power drive for operating said feed wheels.

7. Are apparatus comprising the combination of a base, a column arising from said base, an electrode head supported by said column, a casing having a reflector, means for supporting said base in said casing with said column edgewise towards said reflector, a flange at the edge of said column, a rigid conductor for said head behind said flange, and a flexible conductor connecting said rigid conductor to said head.

8. Arc apparatus comprising the combination of a slide. negative and positive electrode heads on said slide, feed wheels in said positive head,

a reflector casing surrounding said slide and said heads, means for operating said slide, separate means for hand feeding the electrodes in each of said heads and means for releasing said feed wheels, said last three mentioned means bein pmitioned adjacent each other at the same side of said reflector easing.

. 9. Are apparatus comprising the combination of a motor having a shaft, a reduction gearing carried by said motor and having a slow speed shaft extending at right angles to and on opposite sides of said motor shaft, positive and negative electrode heads, means coupling said sicw speed shaft at one side of said motor shaft to one of said heads, and means coupling said slow speed shaft at the other side of said motor shaft to the other of said heads.

l0. Arc apparatus for a reflector casing comprising the combination of a. base plate, means for securing said plate in said reflector casing, a pair of spaced supports on said base, positive and negative heads at the top of said supports, a motor on said base between said supports, a reduction gearing for said motor and having a slow speed shaft, a positive electrode drive shaft extending between said positive head and said slow speed shaft, 8. bearing on said base, a negative electrode drive shaft extending between said negative head and said bearing, and stepping means operatively connecting said reduction gearing and said negative electrode drive shaft.

l1. Arc apparatus comprising the combination of a base, an electrode head, an electrode drive shaft having a plurality of aligned sections arising from said base, a bearing on said base for each of said sections, a steppin device for that one of said sections which is adjacent said base, a connection between the other of said sections and said electrode head, a frictional coupling between said sections, a motor for operating said stepping device, and hand operating means for said section which is connected to said electrode head.

12; Arc apparatus comprising the combination of feed wheels, a scroll gear therefor. and having a peripheral serrations, an adjustable screw engageable with said serrations, a cam follower for operating said scrw and a cam for operating said cam follower, said cam being substantially a circle and arranged about a center abaxial with respect to said scroll gear, and a. driving gear flxed to said cam and frictionally coupled to said scroll gear.

13. Arc apparatus comprising the combination of a. support, a bed at the top of said support, a. slide on said bed, a post on said slide, a positive head on said post, a depending flange on said slide, a negative head on said flange and having its axis arranged substantially at 50 from the axis of said positive head, a screw on said negative head for advancing the negative electrode, a. gear on said screw, a negative electrode drive shaft having a gear meshing with said first mentioned gear and means rotatably supporting said gears behind said post.

14. Are apparatus according to claim 13, comprising bearings on said negative head for both of said gears.

15. Arc apparatus comprising the combination 70 of a slide, a post on said slide, a positive head on said post, a negative electrode drive shaft rotatably mounted in said slide, a depending flange on said slide, a negative head on said. flange, a gear for said negative head, and a gear on said drive shaft above said slide and meshing with said first mentioned gear.

l6. Arc apparatus comprising the combination of a slide having a horizontal portion and a depending portion, a positive head on said horizontal portion, and a negative head on said depending portion, a screw slidably mounted in said negative head, a negative electrode holder movable with said screw, a lever pivotally mounted on said negative head for reciprocating said screw, 9. base having a support for said slide, a strike coil on said base and having an armature, and a rod connecting said armature to said lever.

17. An arc apparatus unit movable for assembly purposes as a unit through the open end of a casing having a cylindrical wall, said unit comprising the combination of a. slide, positive and negative electrode heads on said slide, a pair of upright columns spaced crosswise of the axis of said heads and terminating at their upper ends in a bed for supporting said slide, a base between the lower ends of said columns and secured thereto, a motor on said base, operative connections between said motor and said heads; and means for securing said unit inside of said casi g.

18. An arc apparatus unit according to claim 17 comprising bosses inside of said wall, said means comprising means for securing said base on said bosses. c

19. An arc apparatus unit movable for assembly purposes as a unit through the open end of a casing having a cylindrical wall, said unit comprising the combination of a slide, positive and negative electrode heads on said slide, a pair of upright columns spaced crosswise of the axis of said heads and terminating at their upper ends in a bed for supporting said slide, a base, means for securing the lower ends of said columns on said base, a motor on top of said base, operative connections between said motor and said heads; and means for securing said base adjacent to the inside of said wall.

20. Arc apparatus comprising the combination of a motor having a shaft, a reduction gearing coupled to said motorand having a slow speed shaft extending vertically at right angles to and on opposite sides of said motor shaft, positive and negative electrode heads, means coupling the upper end of said slow speed shaft at the upper side of said motor shaft to said positive head, stepping mechanism for driving said negative head; and means coupling the lower end of said slow speed shaft below said motor shaft to said stepping mechanism.

21. Arc apparatus comprising the combination of a support, a bed at the top of said support, a slide on said bed, a positive head on said slide and having an axis parallel thereto, a. flange depending from said slide and integral therewith and extending substantially at 50 from said slide;

and means on said depending flange for supporting a negative electrode for movement parallel to said depending flange.

HOWARD G. SPEAR. 

